On 1 May Sally owed William $400. On 21 May she purchased

On 1 May Sally owed William $400. On 21 May she purchased goods, list price $1 440, subject to a trade discount of 25%. She returned one third of these goods on 24 May.

How much did Sally owe William on 31 May?

A. $630 

B. $720 

C. $1,030 

D. $1,120